The present invention relates to a carbon fiber having catalytic metal supported thereon.
Conventionally, carbon black on which catalytic metal is supported is known.
This catalyst is manufactured by immersing carbon black in an aqueous solution in which catalytic metal such as platinum particles or platinum alloy particles are suspended and reducing the catalytic metal by heating and stirring, whereby platinum is deposited and supported on the carbon black particles.
Because carbon black has a large diameter of several hundreds of nanometers and deposition of catalytic metal is nonuniform, support efficiency of catalytic metal is poor. This gives rise to a problem that a sufficient catalytic effect cannot be obtained.
The platinum content in the aqueous solution must be increased in order to increase the deposited amount of the catalytic metal. If the platinum content is increased excessively, catalytic metal aggregate and the area of the outer surface of the catalytic metal is decreased. As a result, a desired catalytic effect cannot be obtained. In the case where carbon black is used as the support, catalytic metal is held in a state in which part of the catalytic metal is buried on the outer surface of the support. This decreases the area of the outer surface of the catalytic metal, whereby a satisfactory catalytic effect cannot be obtained.